Recently an engine automatic stop and start system (generally referred to as an idle-stop or idling-stop system) is provided in a vehicle as disclosed in for example, patent document 1 (JP 11-30139A). This system automatically stops an engine when a predetermined automatic stop condition is satisfied, and then automatically starts, that is, restarts, the engine when a predetermined automatic start condition is satisfied.
This starter is configured to engage a pinion gear driven to rotate by a motor to a ring gear of the engine and to energize the motor (drive the motor) by supplying electric current independently of each other.
Since this starter is capable of controlling the pinion gear and the motor independently, the starter is referred to as an independently-controlled starter. In such a vehicle having the idle-stop system (idle-stop vehicle), the independently-controlled starter is used more and more.
More specifically, when the pinion gear is driven to rotate by the starter motor while being engaged with the ring gear of the engine, it rotates the ring gear to crank the engine. In the independently-controlled starter, a pinion control solenoid and a motor control electromagnetic switch are controllable independently. The pinion control solenoid is an actuator that moves the pinion gear from an initial position, at which the pinion gear is disengaged from (not engaged with) the ring gear, to an engagement position, at which the pinion gear is engaged with the ring gear. The motor control electromagnetic switch is a large-sized relay, which conducts a power supply path leading to the motor.
Thus, according to the independently-controlled starter, the pinion gear is engaged with the ring gear by driving the pinion control solenoid, specifically by energizing a coil of the solenoid, before the motor is operated. Then the motor is started to operate with its pinion gear engaged with the ring gear by driving the motor control electromagnetic switch, specifically by energizing a coil of the electromagnetic switch. As a result, wear of the pinion and the ring gear and noise as well as vibration at the time of engagement of the same are reduced.
In the idle-stop vehicle, the engine is stopped and restarted while traveling, including at rest with travel speed being 0. It is therefore preferred to use the independently-controlled starter to reduce the wear, noise and vibration. In addition, even after the engine is controlled to automatically stop, the engine sometimes need be restarted while the engine is still continuing to rotate by inertia with falling rotation. For smoothly restarting the engine, the difference in rotation speeds of the pinion gear and the ring gear should be reduced when the pinion gear engages the ring gear. It is therefore desired that the pinion gear is pushed out for engagement after the motor is driven when the engine rotation speed is high. It is desired that the motor is driven after the pinion gear is pushed out, when the engine rotation speed is low.
In the vehicle including the independently-controlled starter, a control device for the starter drives first the pinion control solenoid and then operates the motor by driving the motor control electromagnetic switch, even in a user start case, in which the engine is started by a manual operation of the user. This user start case is not an automatic engine restart case from the idle-stop condition but an engine start case by a manual start operation of the driver. The idle-stop condition indicates that the engine is being maintained at reset automatically by the idle-stop system.
As proposed in, for example, patent document 2 (JP 2010-90874A, US 2010/0090526 A1), a user start circuit for performing a user start operation may wholly or partly be formed as a circuit, which is separate from an automatic restart circuit for restarting an engine from an idle-stop condition. This circuit arrangement is for improving reliability by redundancy and ensuring a user start operation with low power voltage. More specifically, this user start circuit is so configured that, when a driver turns on a key switch as a starting manual operation with a neutral switch of a transmission being turned on, a solenoid relay for energizing a coil of a pinion control solenoid is turned on with a battery voltage, which is supplied as a user start command signal generated by such a manual operation of the user. Further, a motor relay is turned on after a predetermined delay time of a delay circuit from the turn-on of the solenoid relay.
According to the above-exemplified user start circuit, a pinion gear contacts a ring gear for engagement at higher rotation speeds when the delay time of the delay circuit becomes shorter than a predetermined normal delay time in comparison to a case that the delay time is equal to the normal delay time. The pinion gear and the ring gear wear due to poor engagement between the pinion gear and the ring gear. As the wear progresses, the pinion gear and the ring gear will not be able to engage properly and the engine will not be started. Particularly in the idle-stop vehicle, since the engine is controlled to automatically stop on a travel road, the engine will be disabled to be started again and the vehicle will be disabled to travel again.
It is also not desired that the delay time of the delay circuit becomes longer than the normal delay time. Since the timing of starting the motor operation is delayed more, the startability of the engine is degraded. When the pinion gear contacts the ring gear, it generates hitting sound at timing different from operation sound of a motor. This hitting sound causes a driver of a vehicle (user) to feel discomfort.
In an apparatus for controlling an independently-controlled starter, it is possible to operate a motor by driving a motor control electromagnetic switch after a predetermined delay time from driving first a pinion control solenoid at the time of restarting an engine from an idle-stop condition. If the delay time deviates from a predetermined normal delay time, the above-described adversary operation will arise similarly.